Grinding apparatus for fibrous material

ABSTRACT

Grinding device, more especially a disc refiner for the paper industry; in a housing having two end covers is a rotor and a stator which is displaceable axially relatively to the rotor and guided in nonrotatable manner on the housing; the stator provided with a central opening for the throughflow of the stock to be handled in the grinding device; the stator being under a pressure of the stock to be handled in the grinding device also on that wall which is remote from the rotor; the space which lies between that wall of the displaceable stator which is remote from the rotor and the housing wall is made of substantially cylindrical form and a stock pipe opens tangentially into this space.

United States Patent 11 1 1111 3,831,868 Kahmann Aug. 27, 1974 1 GRINDING APPARATUS FOR FIBROUS 2,947,485 8/1960 Woodruff 241/2592 x MATERIAL 3,158,333 11/1964 Asplund ct a1. 241/244 3,302,893 2/1967 Feder et a1 241/37 [75] Inventor: Albrecht Kahmann, Weingarten,

Germany Primary Examiner-Granville Y. Custer, Jr. [73] Assignee: Escher Wyss G.m.b.H., Ravensburg, Assistant EXaml'er H0Wa-rd Goldberg Germany Attorney, Agent, or FirmRobert A. Ostmann [22] F1led: Sept. 14, 1972 [57] ABSTRACT [21] Appl- 288,945 Grinding device, more especially a disc refiner for the paper industry; in a housing having two end covers is 30 Foreign Application priority Data a rotor and a stator which is displaceable axially rela- Se 1 17 197] German 2146549 tively to the rotor and guided in nonrotatable manner y on the housing; the stator provided with a central [52] U S C] 241/245 241/259 2 opening for the throughflow of the stock to be han- [511 "k 7/02 B020 7/1'4 dled in the grinding device; the stator being under a [58] w /259 l 5 2 259 3 pressure of the stock to be handled in the grinding de- 41/37 2 vice also on that wall which is remote from the rotor;

the space which lies between that wall of the displace- [56] References Cited able stator which is remote from the rotor and the housing wall is made of substantially cylindrical form UNITED STATES PATENTS and a stock pipe opens tangentially into this space. 2,412.681) 12/1946 Fisher et a1. i. 241/2591 2,561,043 7 1951 Ayers 241/245 x 2 Clams, l Drawmg Flgllre 7 $2 8 4 1s 2 2 1g 17 1 27 Z 2 6 8 9 I l; 1 7 Y {1 3 2 Z7 Z2 7 L E F 2 g 5 3- l l A A r GRINDING APPARATUS FOR FIBROUS MATERIAL BACKGROUND OF THE INVENTION The invention relates to a grinding device, more especially a disc refiner for the paper industry; the device comprises, in a housing having two end covers, a rotor and a stator which is displaceable axially relatively to the rotor and is guided in non-rotatable manner on the housing; the stator is provided with a central opening for the throughflow of the stock to be processed in the grinding device; the stator is under a pressure of the stock to be processed in the grinding device also on that wall which is remote from the rotor.

Such grinding devices are used in the paper industry for preparing a stock which is to be used in a paper machine.

The pressure which is to be used in an existing device for the displacement and holding of the displaceable stator in a working position relatively to the rotor is very high. Consequently, the grinding device is so constructed that also that wall of the displaceable stator which is remote from the rotor is under the pressure of the stock to be handled. In this way, the device for the displacement and holding of the stator is substantially relieved of load.

With such prior grinding devices, however, stagnating flow regions are developed in the throughflow stream of the stock, particularly in the space between the housing wall and the wall of the displaceable stator. Fibres which are in the stock are accumulated in these regions and gradually form a solid mass, which finally prevents the stator being displaced.

SUMMARY OF THE INVENTION It is the object of the invention to obviate this disadvantage. This is achieved according to the invention by the fact that the space which lies between'the housing wall and that wall of the displaceable stator which is remote from the rotor is constructed in substantially cylindrical form, and that a stock pipe opens tangentially into this space.

BRIEF DESCRIPTION OF THE DRAWING The invention is hereinafter more fully described by reference to the accompanying drawing. The drawing shows one constructional example as an axial longitudinal section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The grinding device which is illustrated is a tandemdisc refiner. It comprises a cylindrical housing 1 with a first vertical end cover 2 and a second vertical end cover 3. Arranged in the housing 1 is a stator 4 which is fixed on the end cover 2 and a displaceable stator 5. The latter stator 5 is displaceable in a longitudinal axial direction. It is formed with a central opening 6 for the passage of the stock to be handled and is connected by means of spokes 7 to a cylindrical part 8 which is coaxial with the grinding device. The part 8 extends outwardly through a central opening 9 of the end cover 3 and is sealed off from the opening 9. Connecting parts 10 and 1! connect the part 8 to guideways 12, which are arranged on the end cover 3. In this way, the stator 5 can be moved longitudinally and axially but is guided in non-rotatable manner with respect to the housing 1.

A rotor 14 is rotated between the stators 4 and 5. Its shaft 13 is mounted for longitudinal and axial displacement in a bearing house 15 which is fixed on the end cover 2. The shaft 13 is connected for longitudinal and axial displacement to a driving motor, which is not shown. Thus, depending on the position of the displaceable stator 5, the rotor 14 can assume a central position between the two stators 4 and 5. The displacement and holding of the stator 5 is obtained by means of a hy draulic scrvomotor 16, which acts on the part 8.

The stock to be handled in the grinding device is supplied through an opening 17 from a stock pipe 18. The stock pipe 18 opens into the housing 1 into a substantially cylindrical space 19, which is formed between that wall 20 of the displaceable stator 5 which is remote from the rotor 14 and the vertical end cover 3. The pressure under which the stock to be handled is in the chamber 17 acts on the wall 20 and in this way substantially relieves the load on the scrvomotor 16.

The stock pipe 18 feeds the stock to the grinding device and opens tangentially into the space 19. The stock flows through the space 19 and forms herein a circulating vortex. First of all, it flows along the peripheral wall 21 of the space 19, and then helically and always closer in direction to the centre of the space 19. Always still circulating, the stock passes through the opening 6 to the actual processing position between the surfaces of the stators 4 and 5 and the rotor 14 in gaps 25 and 26. The rotor 14 is formed with openings 22 for the passage of the stock to the gap 26. The stock leaves the grinding device through an opening 23 and a stock pipe 24.

The intensive movement, namely, the circulating vortex of the stock in the space 19, is the result of the tangential opening of the stock pipe 18 into the chamber 19, which is still made substantially cylindrical. No stagnating regions of the flow of stock are formed here and the fibres which are in the stock are also entrained without accumulating anywhere and thereby blocking the displacement of the stator 5.

Whereas the stock to be handled is supplied through the stock pipe 18 in the constructional example and, by the procedure described, leaves the grinding device through the opening 6, the gap 25 or through the openings 22 into the rotor 14 and the gap 26 and then through the opening 23, other paths of the stock are conceivable with the grinding device according to the invention.

Thus, for example, after a closing of the openings 22 in the rotor 14 and hence a closing of the opening 23, and an opening of the openings 27 which are in the end cover 2, the path of the stock is as follows: from the opening 17, through the opening 6, the gap 25, the gap 26 and through the openings 27 out of the grinding device.

Among other possibilities which. are still available, it is also possible to visualise a path of the stock in a direction opposite to that which has just been described. In this case also, the circulating vortex, in which the stock leaves the rotor, is maintained in the space 19 because of the cylindrical form of the space 19 and the tangential opening of the stock pipe.

I claim:

1. A grinding device for fibrous stock including a. a housing having two end covers and containing a stator disc which is guided for axial movement relatively to a rotor disc,

b. the stator disc having a front face which cooperates with the rotor disc to define a grinding gap, an opposed rear face, and a central opening,

0. the housing having an internal cylindrical wall which encloses a space bounded at opposite ends by one end cover and the rear face of the stator disc, and being equipped with a stock pipe which opens tangentially into said space from the exterior of the housing;

(1. servomotor means for effecting axial movement of the stator disc and located outside said space, the servomotor means being connected with the stator disc by a cylindrical part which is coaxial with that disc and the housing and projects from the latter through a central opening in said one end cover and is sealed relatively thereto,

e. the whole rear face of the stator disc being subject to the pressure of stock in said space so that the disc is subjected to a force which counteracts the opposing pressure force developed thereon by the stock in the gap and the load on the servomotor means is thereby substantially reduced; and

f. guideway means for guiding the stator disc for said axial movement and located outside said space, the guideway means including cooperating elements connected, respectively, with the housing and the cylindrical part,

g. the central opening, the space and the stock pipe 2. A grinding device as defined in claim 1 in which the stator disc is connected to the cylindrical part by spokes. 

1. A grinding device for fibrous stock including a. a housing having two end covers and containing a stator disc which is guided for axial movement relatively to a rotor disc, b. the stator disc having a front face which cooperates with the rotor disc to define a grinding gap, an opposed rear face, and a central opening, c. the housing having an internal cylindrical wall which encloses a space bOunded at opposite ends by one end cover and the rear face of the stator disc, and being equipped with a stock pipe which opens tangentially into said space from the exterior of the housing; d. servomotor means for effecting axial movement of the stator disc and located outside said space, the servomotor means being connected with the stator disc by a cylindrical part which is coaxial with that disc and the housing and projects from the latter through a central opening in said one end cover and is sealed relatively thereto, e. the whole rear face of the stator disc being subject to the pressure of stock in said space so that the disc is subjected to a force which counteracts the opposing pressure force developed thereon by the stock in the gap and the load on the servomotor means is thereby substantially reduced; and f. guideway means for guiding the stator disc for said axial movement and located outside said space, the guideway means including cooperating elements connected, respectively, with the housing and the cylindrical part, g. the central opening, the space and the stock pipe defining a stock throughflow path which is free of stagnant regions and which effects vortex circulation of stock in said space, whereby the build-up of fiber deposits in said space which would block movement of the stator disc is precluded.
 2. A grinding device as defined in claim 1 in which the stator disc is connected to the cylindrical part by spokes. 